Not Applicable
Not Applicable
The present invention relates to the field of aerosol spray characterization, and more particularly, to computer assisted methods of analyzing and characterizing a set of sequential images corresponding to the progression of an aerosol spray.
The fluid dynamic characterization of the aerosol spray emitted by metered nasal spray pumps and metered dose inhalers is crucial in determining the overall performance of the inhaler as a drug delivery device (xe2x80x9cDDDxe2x80x9d). In addition to treating direct respiratory ailments, inhaler-based DDDs are now increasingly being used to deliver drugs such as flu vaccines, insulin and migraine headache relievers because they deliver their dose of medication to tissues that can more efficiently absorb the drug and bring relief to patients more conveniently. Spray characterization is also an integral part of the regulatory submissions necessary for Food and Drug Administration (xe2x80x9cFDAxe2x80x9d) approval of research and development, quality assurance and stability testing procedures for new and existing inhaler-based DDDs.
Thorough characterization of the spray""s geometry has been found to be the best indicator of the overall performance of most inhaler-based DDDs. In particular, measurements of the spray""s divergence angle (plume geometry) as it exits the device; the spray""s cross-sectional ellipticity, uniformity and particle/droplet distribution (spray pattern); and the time evolution of the developing spray have been found to be the most representative performance quantities in the characterization of an inhaler-based DDD.
During research and development, these measurements are typically used to optimally match the spray pump""s performance characteristics with the fluid properties of the liquid/solid medicine solution, resulting in a more cost-effective and efficient product design. However, accurate, reliable and easy-to-use protocols and a system for inhaler-based DDDspray characterization do not exist. During quality assurance and stability testing, plume geometry and spray pattern measurements are key identifiers for verifying consistency and conformity with the approved data criteria for the inhaler-based DDD.
The currently adopted inhaler spray testing standard that is in use today at pharmaceutical companies involves firing the spray pump at a solid, thin-layer chromatography (xe2x80x9cTLCxe2x80x9d) plate having a coating that fluoresces in response to incident ultraviolet (xe2x80x9cUVxe2x80x9d) radiation. The TLC plate is positioned at a fixed height above the exit port of the pump. The pattern of the spray deposited on the plate is then analyzed.
In a conventional test configuration, the analysis of an exposed plate begins with illumination of the plate with UV radiation. The incident UV radiation causes the plate""s coating to fluoresce and helps to highlight the outline of the spray pattern. Marking instruments and mechanical calipers are then used to draw and measure an outline of the deposited patterns on the plate. Measurements of the spray pattern""s ellipticity in terms of major- and minor-diameters are recorded.
One disadvantage to this configuration is that the presence of the TLC plate radically alters the natural fluid dynamics of the spray causing it to switch from a free aerosol jet to an impinging jet.
Another disadvantage to this configuration is that a large of amount of the spray particles bounce off the plate, causing artifacts in the pattern that do not exist in an unconstrained spray. This is especially problematic for dry powder-based DDDs because the particles don""t tend to stick to the TLC plate at all causing artificially low spray pattern densities to be measured and reported.
Yet another disadvantage to this configuration is that the measurements of the spray pattern are very sensitive to the operator""s judgement and prone to low reliability.
A further disadvantage to this configuration is that the associated measurement technique is restricted to measurements only of the static aspects of the spray pattern; it cannot be used to investigate any time-evolving or plume geometry properties of the spray.
It is an object of the present invention to substantially overcome the above-identified disadvantages and drawbacks of the prior art.
The current invention provides an imaging and analysis system that receives information representative of the time evolution of an aerosol spray, displays individual and sequential images of the spray with respect to various observation angles, and characterizes parameters relating to the spray, such as the spray plume central axis, divergence angle and cross-sectional uniformity and ellipticity. In a preferred embodiment, the imaging and analysis system includes software running on a general purpose computer system.
The foregoing and other objects are achieved by the invention which in one aspect comprises a method of analyzing image data representative of a sequential set of images of a spray plume, each of the images being representative of a density characteristic of the spray plume (i) along a geometric plane that intersects the spray plume, and (ii) at a predetermined instant in time. The method includes sequentially displaying the set of images so as to exhibit a time evolution of the spray plume along the geometric plane, and measuring one or more spray plume parameters associated with the spray plume within one or more of the images.
In another embodiment of the invention, the one or more parameters includes the central axis of the spray plume.
In another embodiment of the invention, the one or more parameters further includes an angle measured from the central axis of the spray plume to an outer boundary of the spray plume.
In another embodiment of the invention, the one or more parameters includes one or more cross-sectional axes of the spray plume.
Another embodiment of the invention further includes superimposing a shape upon the one or more images so as to delineate an area of the spray plume, and measuring one or more spray plume parameters within the area.
In another embodiment of the invention, the spray plume parameters are selected from the group consisting of area start X and Y coordinates, area end X and Y coordinates, area width, area height, mean spray intensity, spray standard deviation, minimum spray intensity, maximum spray intensity, and spray intensity histogram.
Another embodiment of the invention further includes superimposing a line upon the one or more images so as to delineate an axis of the spray plume, and measuring one or more spray plume parameters along the axis.
In another embodiment of the invention, the spray plume parameters are selected from the group consisting of axis start X and Y coordinates, axis end X and Y coordinates, axis length, axis width, axis height, axis angle, mean spray intensity, spray standard deviation, minimum spray intensity, maximum spray intensity, and spray intensity profile.
Another embodiment of the invention further includes inserting one or more calibrating components associated with displaying the images so as to associate physical coordinates with image coordinates within each of the set of images.
Another embodiment of the invention further includes integrating the set of images so as to exhibit a time-average representation of the images, and measuring one or more parameters of the time average representation.
In another embodiment of the invention, the time-average representation of images corresponds to an axial cross-sectional density characteristic along a geometric plane substantially normal to a flow direction centerline, such that the step of integrating produces a cross-sectional spray pattern image.
In another embodiment of the invention, the time-average representation of images corresponds to a longitudinal density characteristic along a geometric plane substantially parallel to and intersecting the flow direction centerline, such that the step of integrating produces a longitudinal plume image.
Another embodiment of the invention further includes subtracting a first in time image of the set of images from the time-average representation, so as to remove one or more common image components of the set of images from the time average representation.
In another aspect, the invention comprises a system for analyzing image data representative of a sequential set of images of a spray plume, each of the images being representative of a density characteristic of the spray plume (i) along a geometric plane that intersects the spray plume, and (ii) at a predetermined instant in time. The system includes a processing device for receiving the set of images, and sequentially displaying the set of images so as to exhibit a time evolution of the spray plume along the geometric plane. The system further includes a controller, associated with the processing device, that provides a user interface for controlling the processor to measure one or more spray plume parameters associated with the spray plume within one or more of the images.
In another embodiment of the invention, the one or more parameters includes the central axis of the spray plume.
In another embodiment of the invention, the one or more parameters further includes an angle measured from the central axis of the spray plume to an outer boundary of the spray plume.
In another embodiment of the invention, the one or more parameters includes one or more cross-sectional axes of the spray plume.
In another embodiment of the invention, the controller further (i) superimposes a shape upon the one or more images so as to delineate an area of the spray plume, and (ii) measures one or more spray plume parameters within the area.
In another embodiment of the invention, the spray plume parameters are selected from the group consisting of area start X and Y coordinates, area end X and Y coordinates, area width, area height, mean spray intensity, spray standard deviation, minimum spray intensity, maximum spray intensity, and spray intensity histogram.
In another embodiment of the invention, the controller further (i) superimposes a line upon the one or more images so as to delineate an axis of the spray plume, and (ii) measures one or more spray plume parameters along the axis.
In another embodiment of the invention, the spray plume parameters are selected from the group consisting of axis start X and Y coordinates, axis end X and Y coordinates, axis length, axis width, axis height, axis angle, mean spray intensity, spray standard deviation, minimum spray intensity, maximum spray intensity, and spray intensity profile.
Another embodiment of the invention further includes one or more calibrating components for associating physical coordinates with image coordinates within each of the set of images.
In another embodiment of the invention, the processor further integrates the set of images so as to exhibit a time-average representation of the images, and measuring one or more parameters of the time average representation.
In another embodiment of the invention, the time-average representation of images corresponds to an axial cross-sectional density characteristic along a geometric plane substantially normal to a flow direction centerline, such that the step of integrating produces a cross-sectional spray pattern image.
In another embodiment of the invention, the time-average representation of images corresponds to a longitudinal density characteristic along a geometric plane substantially parallel to and intersecting the flow direction centerline, such that the step of integrating produces a longitudinal plume image.
In another embodiment of the invention, the processor further subtracts a first in time image of the set of images from the time-average representation, so as to remove one or more common image components of the set of images from the time average representation.
In another embodiment of the invention, the processing device includes a computer system executing software operative to analyze the image data.